1. Field of the Invention
This invention generally relates to a bicycle rear derailleur. More specifically, the present invention relates to a bicycle rear derailleur that adjusts an angular position of the base member and/or an angular position of the chain guide when the bicycle rear derailleur is shifted.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. In particular, the bicycle transmission has been significantly changed over the years.
Derailleur operated bicycle transmissions typically comprise a plurality of sprockets that rotate with another rotating member (e.g., the front crank and/or the rear wheel of the bicycle) and a derailleur that is used to shift a chain among the plurality of sprockets. Conventional derailleur transmissions were manually controlled by a hand operated actuator such as a lever or twist-grip attached to the bicycle handlebar, wherein the derailleur is connected to the actuator by a Bowden cable.
Recently, bicycles have been equipped with electrical components to make riding easier and more enjoyable for the rider. Some bicycles are equipped with electrically controlled shifting systems. In particular, in theses electrically controlled shifting systems, the front and rear derailleurs are provided with motors that laterally move the chain guide to obtain the various gear positions. In the case of a rear derailleur, the angular position of the base member with respect to the frame and the angular position of the chain guide with respect to the movable member are adjusted during a gear changing operation by a pair of springs. While this arrangement generally works quite well, the required adjustment amount for each gear can vary such that the angular positions of the base member and the chain guide will not be optimal for each of the gears.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle rear derailleur. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.